Inflating a Thin VMDK to a thick VMDK is easy, just browse your Datastore, select the VDMK file you want to inflate, right mouse click on it and select inflate.
Note: Your Virtual Machines needs to be powered off and inflating a disk can take-up some time. In my test I inflated a 5 GB Thin disk on witch 3,6 GB was occupied took 8 minutes.This was on a NetApp with Fiber Channel (1GB).

But what if we want to do the opposite? There are a few way to create a Thin VMDK file:

Create a Virtual Machine

Clone to a template

Clone a Virtual Machine

Use VMware Storage VMotion to migrate the virtual machine storage

So, the most easy way to migrate a Thick VMDK file to a Thin VMDK file is to use Storage VMotion.

Right click the Virtual Machine and select Migrate

Select change datastore

Select the Lun you want to move the Virtual Machine to

Select the format. This will be Thin provisioned format of course

Select finish

That’s all

About MichaelMichael Wilmsen is a experienced VMware Architect with more than 20 years in the IT industry. Main focus is VMware vSphere, Horizon View and Hyper Converged with a deep interest into performance and architecture.
Michael is VCDX 210 certified, has been rewarded with the vExpert title from 2011, Nutanix Tech Champion and a Nutanix Platform Professional.